The present invention is directed to a runner for use in a suspended ceiling system, which runner has an expansion joint to provide controlled buckling of the runner if subjected to elevated temperatures due to a fire.
To obtain a fire rating for a suspended ceiling section, various approaches have been taken for providing a runner with a fire-rated expansion section. An example is disclosed in U.S. Pat. No. 3,397,501, wherein a web has an elongated slot adjacent a bead with three spaced cuts extending into the bead from the slot and the web adjacent to the flanges has a second elongated cut so that when subjected to compressive forces the bead will buckle upward as the flanges buckle downward and the web between the two cuts buckles outwardly to one side. Similar proposals are disclosed in U.S. Pat. No. 3,589,089 and U.S. Pat. No. 4,601,153.
Other fire-rated runners have had an opening formed through the web of the runner adjacent the flange and have had the bead completely cut away above the opening so that the web and flange can buckle. Examples are disclosed by U.S. Pat. Nos. 3,159,252; 3,388,519; and 3,965,632.
Another approached for providing expansion joints in an inverted T member is to provide apertures in the webs and to crimp or deform a portion of the bead to aid in causing the bead to buckle. Examples are disclosed by U.S. Pat. Nos. 3,846,031; 3,965,631; 4,598,514; and 4,685,262.
Another type of fire-rated runner has cuts or slits in the web adjacent the flange and has a weakened bead due to either holes or removing portions of the beads. Examples are disclosed by U.S. Pat. Nos. 3,807,111; 4,016,701; and 4,128,978.
In the final catagory, the inverted T has portions of the webs removed adjacent the flange with a portion of the head being deformed and also a portion of the deformed bead being cut away to form a weakened area. Examples are disclosed in U.S. Pat. Nos. 3,778,947 and 4,685,262.